Introduction

Percutaneous transluminal renal angioplasty hasemerged as the treatment of choice in suitable patientswith renovascular hypertension [1, 2, 3, 4, 5, 6]. Thetechnical and clinical success rates range between 80and 100 % for various aetiologies [1, 2, 3, 4, 5, 6, 7]. Theoverall complication rate is low [8]. Various approaches,including femoral, brachial, and axillary, have been usedto gain access to the diseased artery [11 2].

The conventional exchange technique, in which theartery is engaged by a diagnostic catheter which is thenexchanged with a balloon catheter over an exchangeguidewire, is most widely used. The coaxial approach isnot widely used, because most balloon catheters aremounted on 5- to 6-F shafts. These need large-calibreguiding catheters for coaxial passage. A balloon onwire and low, profile balloon catheters on smaller 3.7 to4-F shafts have recently become available for use by co-axial technique. Smaller-diameter coronary angioplastycatheters are also available, mounted on 2.8- to 3.7-Fshafts.

Tight stenosis, especially if ostial and accompaniedby stenosis of perirenal aorta and periarterial fibrosis,as in patients with nonspecific aortoarteritis, can be dif-ficult to engage and cross with the balloon catheter [3,9]. The whole assembly tends to buckle into the aortaduring attempts to cross the stenosis with balloon cathe-ter, because of acute angulation at the junction of theaorta and the renal artery, lack of back-up support atthis point, and inadequate purchase from the distal partof the exchange guidewire. In this study we evaluatethe utility of coaxial technique in this subset of patients.

Materials and methods

During a 7-year period 132 consecutive renal arterystenoses in 87 patients were subjected to percutaneoustransluminal renal angioplasty. The stenosis was causedby nonspecific aortoarteritis (Takayasu's arteritis) in 76

Eur. Radiol. 9, 1586±1589 (1999) Ó Springer-Verlag 1999

EuropeanRadiology

Original article

Utility of coaxial technique for renal angioplastyin patients with a difficult-to-cross stenosisS. Sharma1, M. Mahapatra1, S. Bhargava2, B. Bhargava4, S. Ramamurthy2, M. Rajani1

1 Department of Cardiovascular Radiology, Cardiothoracic Centre, All India Institute of Medical Sciences, IND-110029 New Delhi, India2 Department of Cardiology, Cardiothoracic Centre, All India Institute of Medical Sciences, IND-110029 New Delhi, India

Received: 7 May 1998; Revision received: 10 November 1998; Accepted: 25 November 1998

Abstract. The aim of this study was to evaluate thefeasibility of coaxial approach in difficult-to-cross le-sions in patients with failed percutaneous translumi-nal renal angioplasty by conventional over-the-wireexchange technique. Twelve stenoses in 10 patients(six women and four men; age range 19 � 7 years)with uncontrolled hypertension were treated by thismethod. The stenosis was caused by nonspecific aor-toarteritis in 8 patients and fibromuscular dysplasiain 2 patients. It was ostial in seven and post-ostial infive vessels. Conventional exchange technique wasunsuccessful in all of them. All procedures weredone by femoral route. Technical success was seen in11 (92 %), without complication. The stenosis im-proved from 90 � 2.1 % (range 80±100 %) to 6 � 7 %(range 0±20 %), blood pressure decreased from198 � 12.3 mm Hg (range 180±220 mm Hg)/130 �6.7 mm Hg (range 120±140 mm Hg) to 119 � 5.7 mmHg (range 110±130 mm Hg)/83 � 3.9 mm Hg (range80±90 mm Hg), and number of drug treatments forhypertension fell from 3.6 � 0.52 (range 3±4) to1 � 0.94 (range 0±3; p < 0.01). Percutaneous translu-minal renal angioplasty resulted in ªcureº in 3 pa-tients and ªimprovementº in 7 patients. Follow-upperiod was 3±21 months (mean 6.4 months). No rest-enosis was detected. Coaxial approach is safe and ef-fective in treating difficult-to-cross lesions in whichrenal angioplasty by conventional exchange tech-nique is unsuccessful.

Key words: Aortic arch syndrome ± Arteries ± Renaltransluminal angioplasty ± Arteritis ± Hypertension± Aortitis ± Takayasu's arteritis ± Fibromuscular dys-plasia

Correspondence to: S. Sharma

patients, atherosclerosis in 8 patients, and fibromusculardysplasia in 3 patients. The technique has been reportedpreviously [3, 9]. Among them, 10 patients, in whomconventional exchange technique failed to relieve theobstruction, were treated by coaxial technique. In thisgroup there were six women and four men (age range6±28 years (mean 18.7 � 7.4 years). The stenosis wascaused by nonspecific aortoarteritis in 8 patients and fi-bromuscular dysplasia in 2 patients.

The diagnosis of nonspecific aortoarteritis was basedon the following criteria [10, 11]: (a) symptoms causedby ischemia of the central nervous system, upper ex-tremities, or kidneys; fever, absent or decreased pulses,bruits, and fundoscopic findings; (b) laboratory findings,including raised sedimentation rate and antistreptol-ysin-O titer and positive C-reactive protein test; and (c)angiographic findings, including a spectrum of changesranging from minimal intimal irregularity to typical rat-tail narrowing, complete obstruction, dilatation, or an-eurysm formation in the involved blood vessel. Involve-ment of the aorta and its medium-sized branches, or in-volvement of at least two medium-sized branches, wasconsidered essential for diagnosing nonspecific aortoar-teritis. Conditions such as Buerger's disease, atheroscle-rosis, thromboembolism, collagen vascular disease, andcongenital vascular malformation were excluded. Nopathologic confirmation of the diagnosis was obtainedin any patient. All angiograms were performed by a per-cutaneous transfemoral route according to a previouslyreported protocol [12].

The clinical indication for treatment by renal angio-plasty was systemic hypertension, uncontrolled on sin-gle-drug therapy in the presence of > 70 % stenosis inthe renal artery and, in patients with nonspecific aorto-arteritis, the presence of clinically inactive disease.

Patients were pre-treated with oral aspirin (175 mg)before angioplasty, and this regime was continued dailyfor 6 months after treatment. Informed written consentwas obtained. All procedures were performed by percu-taneous transfemoral route. At the beginning of the pro-cedure, an indwelling sheath was placed in the groin.Heparin (100 IU/kg body weight) was given intrave-nously at this stage. Initial attempts to treat the stenosiswere made by the standard exchange technique whichis discussed in detail elsewhere [3, 8]. Briefly, this includ-ed engaging the diseased renal artery by a preshaped di-agnostic catheter, crossing the stenosis with a J-shapedhydrophilic guidewire (Terumo Corporation, Tokyo, Ja-pan) and then exchanging the diagnostic catheter withan appropriate-sized balloon catheter (Schneider, Zu-rich, Switzerland; or Boston-Scientific, Watertown,Mass.) over a non-hydrophilic exchange guidewire(Boston-Scientific).

When this approach failed, the diseased renal arterywas reengaged with a 6- or 7-F superflow right coronaryguiding catheter (Schneider, Zurich, Switzerland). Wedid not use a renal guiding catheter due to its nonavail-ability. The stenosis was crossed with a 0.014-or 0.018-inch-wide guidewire with the back-up support of an ap-propriate-sized balloon catheter (Schneider, USA, orBoston-Scientific, Watertown, Mass). A test injection

was made from the guiding catheter to ensure intralumi-nal position of the guidewire across the stenosis in therenal artery. The balloon was then advanced into the re-nal artery distal to the stenosis, the guidewire was re-moved, and a pressure gradient was measured. Theguidewire was then reinserted in the distal renal artery,the balloon catheter was withdrawn into the stenoticsegment, and its position was confirmed by injection ofcontrast material from the guiding catheter. The balloonwas inflated by injecting diluted contrast material (onepart contrast material and three parts of normal saline)from a pressure induflator through the side port, untilthe waist was no longer present, for up to 45 s.

The diseased renal arteries/branches measured2±5 mm. This measurement was made in the prestenoticsegment or 2 cm beyond the stenosis to exclude the seg-ment with poststenotic dilatation. Consequently, theballoon diameters ranged from 2.5 to 5 mm, and infla-tion pressures were up to 16 atm to remove the waist.We chose same-sized balloon diameters for treatmentby angioplasty. A low-pressure inflation at 4 atm for60 s was subsequently performed to tack the intima.

Immediately after the procedure, the transstenoticpressure gradient was measured, and a diagnostic angio-gram was performed to assess the adequacy of angio-plasty. Angioplasty was considered technically success-ful if (a) the arterial lumen after angioplastyhad < 30% residual stenosis, with at least 50% increasein its pretreatment diameter; and (b) the pressure gradi-ent was < 20 mm Hg.

The clinical results of angioplasty were judged as fol-lows: (a) ªcureº (normal blood pressure after the proce-dure without antihypertensive drug therapy); (b) ªim-provedº (at least 15% reduction in diastolic blood pres-sure or a diastolic pressure less than 90 mm Hg with thepatient taking less antihypertensive medication than be-fore the procedure); and (c)ºfailedº (no change in bloodpressure after the procedure) [1, 2]. All patients ªcuredºor ªimprovedº were considered to have benefited fromangioplasty. Follow-up examination included bloodpressure and medication evaluation at 1-week, 4- to6-week, and 6-month intervals thereafter.

Results

The procedure was technically and clinically successfulin 11 (92 %) stenoses (Figs. 1, 2). In 1 patient the lesionwas crossed with the guidewire but the balloon couldnot be negotiated across the stenosis. No major compli-cation was encountered.

The stenosis involved the right renal artery in 6 pa-tients, left renal artery in 2 patients, and was bilateralin 2 patients. It began at the ostium, extending for a vari-able length up to 3 cm in 7 patients and was located inthe post-ostial segment in five instances. All patients ex-perienced intense, transient backache during balloon in-flation, which subsided soon after the balloon was de-flated.

Following percutaneous transluminal renal angio-plasty, the stenosis decreased from 90 � 2.1 % (range

S.Sharma et al.: Utility of coaxial technique for renal angioplasty 1587

80±100 %) to 6 � 7% (range 0±20 %; p < 0.01), the pres-sure gradient decreased from 94 � 14.4 mm Hg (range70±120 mm Hg) to 5 � 5.4 mm Hg (range 0±20 mm Hg;p < 0.01), blood pressure fell from 198 � 12.3 mm Hg(range 180±220 mm Hg)/130 � 6.7 mm Hg (range120±140 mm Hg) to 119 � 5.7 mm Hg (range110±130 mm Hg)/83 � 3.9 mm Hg (range 80±90 mmHg) within 24 h (p < 0.01). The number of drugs re-quired for control of hypertension decreased from3.6 � 0.52 (range 3±4) to 1 � 0.94 (range 0±3; p < 0.01).

The procedure resulted in clinical ªcureº of hyper-tension in 3 patients and ªimprovementº in 7 patients.The follow-up period ranged from 3 to 21 (mean, 6.4)months. Restenosis, as evidenced by recurrence of hy-pertension, increase in drug requirement for control of

hypertension, or angiographic demonstration of rest-enosis, was not detected in any patient. Follow-up angi-ograms were performed in five patients.

Discussion

Our results confirm the utility of coaxial technique dur-ing angioplasty in difficult-to-cross renal artery stenosisby the conventional guidewire exchange method. Thistechnique is safe, effective, and more convenient. It hasmany advantages. The presence of back-up support bythe guiding catheter at the renal artery ostium and avail-ability of additional back up from the balloon catheterare helpful in negotiating tight stenosis, especially if itbegins at the ostium and is associated with perirenal aor-tic stenosis. Often, the disease extends across a renal ar-tery branch with or without its involvement, necessitat-ing the introduction of a guidewire in the branch for itsªprotectionº during balloon inflation in the parent ves-sel or subsequent dilatation.

At other times with distally located stenosis, the diam-eter of the involved artery is small and needs a 2.5- to4-mm balloon catheter. These smaller-diameter cathe-ters are usually mounted on 2.8- to 3.8-F shafts and areusually unsuitable for exchange over the wire unlessback-up support is available. In such situations the pres-ence of a guiding catheter is necessary for proper posi-tioning of the guidewire and balloon catheter. The feasi-

S.Sharma et al.: Utility of coaxial technique for renal angioplasty1588

1a

1b

2a

2b

Fig.1. a A 28-year-old wom-an with uncontrolled hyper-tension. Selective right renalangiogram in the anteropos-terior view shows a shortsegment, tight stenosis withpost-stenotic dilatation.b Plain radiograph in thesame view shows the guidingcatheter in the right renal ar-tery with an inflated ballooncatheter over a guidewireacross the stenosis. c Post-angioplasty angiogram in thesame view shows normalisa-tion of arterial calibre

Fig.2. a A 22-year-old wom-an with uncontrolled hyper-tension. Selective right renalangiogram in the anteropos-terior view shows a proxi-mal, tight stenosis in the re-nal artery with post-stenoticdilatation. b Aortogram inthe same view after angio-plasty shows good openingof the lesion with mild resid-ual stenosis

1c

bility of repeated test injections during guidewire andballoon catheter manoeuvring, and for check angiogra-phy immediately after angioplasty with the ballooncatheter across the stenosis, are additional advantagesof the guiding catheter. It can also deliver drugs such astrinitroglycerine directly into the involved vessel for in-stantaneous local action. This technique is also time sav-ing because the need for catheter exchange every timeafter balloon inflation is obviated and instantaneous im-ages can be obtained to assess the adequacy of angio-plasty.

The major disadvantage of this technique is its cost.Even though the use such hardware facilitates the pro-cedure, each item including the guiding catheter, 0.014-inch-wide guidewire, Toohey-Borst, and the 2.5- to4-mm-wide balloon catheters are expensive. For thisreason, we reserve the use of this technique for onlythose cases in which the conventional exchange tech-nique fails.

Alternatively, such lesions can also be approached byleft axillary or brachial route. The reversal of acute an-gulation of the renal artery origin when viewed fromabove, as in approaches from the arm, can help in guid-ing the balloon catheter into the renal artery. Indeed,this approach has been used in difficult-to-cross lesions,with variable success rates [1, 2]. However, the frequentsteno-obstructive involvement of the subclavian arteryby the disease process in nonspecific aortoarteritis pre-cluded the use of this approach in our patients.

Most patients in this study had nonspecific aortoarte-ritis as the underlying cause of renal artery stenosis. Thisdisease is a rare form of primary arteritis of unknowncause which involves the aorta, its major branches, andthe pulmonary arteries, and results in steno-obstructiveor dilative lesions in involved segments [12, 13]. It ischaracterised by panarteritis involving all layers of thevessel wall [12, 13, 14]. Underlying chronic inflamma-tion, panarteritis, extensive periarterial fibrosis, thick-ening, and adhesions combine to produce tough, non-compliant, and rigid vessel walls. The resultant stenosismost frequently involves the peri-renal aorta and the re-nal arteries, resulting in renovascular hypertension [12].The renal artery often arises from a stenosed segmentand has a stenosis beginning at its origin and extendingfor a variable length. This was also the case in most pa-tients in this study. This angiographic morphology com-bined with the tough nature of the lesions producestechnical problems during angioplasty [3, 9, 15]. Such le-sions are difficult to engage and resist prolonged, re-peated mechanical distension before responding to bal-loon dilatation. In this setting, the use of the coaxialtechnique and balloon catheters which can withstandhigh inflation pressures offer distinct advantages. Theresults of the present study validate this observation.

We conclude that the coaxial technique can be a use-ful alternative approach during renal angioplasty in se-

lected patients with difficult-to-cross lesions. It has ahigh technical success rate and the complication rate islow. It should be considered in situations where the con-ventional exchange technique for angioplasty is unsuc-cessful. Cost remains its major disadvantage.

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